In the operation of commercial aircraft, it is necessary to provide on-board toilet facilities for use by the passengers and crew. These toilet facilities include vacuum toilets which presently require a specific amount of water to operate. However, an aircraft has only one limited water supply to meet all the water needs of the passengers and crew during the flight of the aircraft for drinking, food preparation, and other uses, as well as for use by the aircraft toilets. The amount of water stored in the aircraft is proportional to the trip duration and the number of passengers and crew that will be on-board the aircraft. Further, an ample amount of water is necessary to ensure the comfort of the passengers and crew. Unfortunately, a large amount of fuel is required just to transport the water supply which is a significant operational cost and decreases the efficiency of the aircraft. Therefore, a need exists to reduce the amount of water required to be flown by the aircraft to increase the overall efficiency of the aircraft and reduce operational costs.
As previously discussed, a significant amount of water is used during any given aircraft flight to operate the aircraft toilets. A reason for this is that when the toilet is flushed, no differentiation is made between flushing with solid matter due to defecation, and without solid matter, such as when a man stands and urinates. When the toilet is flushed, a standard amount of water is always used, approximately 8 fluid ounces, which assumes that solid matter, such as tissues and feces, is present. This large amount of water is necessary, when solid matter is present, because if a lesser amount of water is used, deposits will rapidly build upon the walls of the connecting conduits and critically impair the operation of the toilet system. However, when a male uses the toilet to urinate, substantially less water is required for flushing, and using a standard amount of water is excessive. The applicants estimate that approximately 45% of toilet use is by men standing and urinating resulting in a large amount of wasted water. Thus, aircraft currently carry a large load of unnecessary water, and correspondingly use a significant amount of unnecessary fuel to transport it. Therefore, it would be beneficial to have an aircraft toilet system that can vary the amount of flush water used depending upon whether the user has urinated or defecated.
An apparatus to control the amount of water used in the flushing of a toilet is described in U.S. Pat. No. 4,707,867 to Kawabe et al. The Kawabe apparatus utilizes a light beam sensor to detect whether a person has sat upon a toilet seat and uses this information to determine the volume of flush water to be used. The light beam sensor emits a light beam to a reflector which reflects the light beam back to the sensor creating an unbroken horizontal light beam path. The light beam sensor and reflector are located slightly above the toilet such that the light beam path is correspondingly located at the same position. Hence, when a user occupies the toilet, the light beam can neither reach the reflector nor be reflected back to the sensor, and the sensor thereby detects the presence of a user seated on the toilet. If the light beam is interrupted for greater than 90 seconds, the apparatus assumes the toilet user has defecated and utilizes a large amount of water, otherwise, the apparatus assumes the toilet user has urinated and utilizes a small amount of water. This apparatus uses a complicated electronic circuit having a plurality of different timers, which are used to time the interruption of the light beam and to control the timing of the opening and closing of a flush valve, thereby controlling the amount of water used. Although, this type of apparatus works well for its intended purpose, it has many drawbacks that would make it unsuitable for use in an aircraft toilet system.
A disadvantage of the Kawabe apparatus is that it is not suitable for use with aircraft because the aircraft lavatory system, as well as, the aircraft toilet system, would have to be substantially altered to accommodate it. For example, the light beam sensor would have to be mounted to one wall of the aircraft lavatory and the reflector would have to be mounted to another wall of the aircraft lavatory. Also, this type of light beam sensor is likely to become contaminated over time and require servicing. Furthermore, the use of a light beam sensor requires a complicated and expensive electronic circuit which has a plurality of different timers to time the interruption of the light beam. Lastly, another disadvantage of this apparatus, is that the sensor, the electronic circuit, and the associated wiring, could potentially cause electromagnetic interference with the existing on-board electronics of the aircraft. Therefore, the addition and integration of the Kawabe apparatus to an aircraft lavatory and toilet system could be costly and could potentially require additional testing and retrofitting to verify that it does not interfere with the already existing on-board electronics of the aircraft. Thus, the Kawabe apparatus is just not readily adaptable for use with an aircraft.
Accordingly, it should be appreciated that there is a need for a system for reducing water consumption in a vacuum toilet, suitable for use in an aircraft, that detects whether a toilet user has sat on the toilet seat, or has stood, and uses that information to control either a longer or shorter period of flow of rinse water allowing for a significant reduction in average water consumption.